Susan R. Breon - NASA Goddard Space Flight Center, Greenbelt, Maryland 20771
Richard A. Hopkins and Stephen J. Nieczkoski - Ball Electro-optics/Cryogenics Division, Boulder, Colorado
The X-ray Spectrometer (XRS) is an instrument on the Advanced X-ray Astrophysics Facility (AXAF), the third of NASA's Great Observatories scheduled for launch in 1998. The XRS detectors have a resolution of approximately 10 eV over the range 0.3 - 10 keV. To achieve this resolution, the detectors are maintained at or below 0.1 Kelvin using an adiabatic demagnetization refrigerator inside a superfluid helium dewar. In addition, split-Stirling-cycle mechanical coolers are used to extend the anticipated on-orbit helium lifetime to a minimum of 4 years. This paper describes the challenges of developing this hybrid cryogenic system and presents an overview of the current design of the system.
Advances in Cryogenic Engineering 37, pp. 1193-1200, (1992).